A company tax rate cut to 25 per cent hinges on Pauline Hanson and two independent senators sealing a deal with the Turnbull government.
Pauline Hanson is a step closer to voting for corporate tax cuts after getting money for 1000 apprenticeships, but two key independent senators remain on the fence.
One Nation secured funding for the apprenticeships, which are aimed at training young people in regional areas, but likely won't vote for the government's company tax cuts until big employers promise to lift wages.
A deal may have to wait until the senate returns next week, with independents Derryn Hinch and Tim Storer still undecided.
The government needs both their votes and One Nation's three senators to get its plan to cut company tax to 25 per cent through the upper house.
Senator Hanson told reporters on Thursday morning a Business Council letter promising more investment in exchange for tax cuts "does help, very much so."
Senator Hinch wants to see the big banks exempt from the tax cuts, and also wants a promise businesses will lift wages.
"How do you justify giving a five percentage point tax cut to the big banks when there is a royal commission going on?" he said.
Finance Minister Mathias Cormann sent him a letter overnight to address the crossbencher's concern over "sluggish" wages.
"There was some good stuff in it but it doesn't get it over the line," Senator Hinch told reporters.
The letter from big businesses committing to invest more to create jobs hasn't convinced him either.
"The Business Council letter was very 'kumbayah' - we'll do this and we'll do that, but it didn't guarantee anything," Senator Hinch said.
But the key crossbench senator says he is still listening.
The government needs support from nine of 11 Senate crossbenchers - they have Cory Bernardi, David Leyonhjelm, Steve Martin and Fraser Anning all promising to vote for it, and three One Nation senators appear close to the line.
Senator Storer - in his first week in the Senate - now looms as a key swing vote for the $65 billion cuts.
The independent, who quit the Nick Xenophon Team, has not responded to requests for comment.
Labor Senator Doug Cameron urged crossbenchers to "really take a close look at themselves and not just capitulate to "a letter that means nothing" from big businesses.
Greens leader Richard Di Natale said the big business pledge was "totally meaningless".
The government still hopes to put the legislation to a vote before Easter.
Bill Shorten said the government was "in love with the big end of town".
"Let's tell the truth here, some of the biggest companies in Australia don't even pay tax," he told reporters.
But Prime Minister Malcolm Turnbull said Australia needed a lower corporate rate to keep attracting investment.